<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>首页</title>
  </head>
  <body>
    <h1>首页</h1>
    <button>点击获取用户数据</button>
    <script>
      btn = document.querySelector("button");
      btn.onclick = function () {
        const xhr = new XMLHttpRequest();
        // 满足同源策略 url可以简写
        xhr.open("GET", "/data");
        xhr.send();
        xhr.onreadystatechange = function () {
          if (xhr.readyState == 4) {
            if (xhr.status >= 200 && xhr.status < 300) {
              console.log(xhr.response);
            }
          }
        };
      };
    </script>
  </body>
</html>
